How to Fertilize Iris 'Top Flight'?
Diluted iris feed every three to four weeks during spring bloom

Iris 'Top Flight' · Iris 'Top Flight'
Grow in well-drained, fertile, neutral to slightly acidic soil in full sun. Do not cover the rhizomes with mulch, or allow other plants to shade them; sun on the rhizomes encourages flowering. Give a high potash feed in spring and divide every three to four years. See also bearded iris cultivation
Diluted iris feed every three to four weeks during spring bloom